The invention relates to a device for regulating the idling speed of an internal combustion engine.
The device for regulating the idling speed of an internal combustion engine by controlling the feed has an electromechanical setting member which is provided with an electric drive member and at least one magnetic-flux-conducting element between the drive member and a valve element and has at least one return spring which acts on the drive member.
Devices are used to regulate the idling speed in order, in particular in the case of automotive vehicles, to set the lowest possible speed of rotation which results in favorable consumption and emission values. With constant feed of the internal combustion engine, variations in idling speed may occur due, in particular, to different loads caused by auxiliary units. In addition to this, at low idling speed the operating condition of an internal combustion engine is close to the unstable speed range within which the engine may stall upon further additional load. For this reason, the rate of flow of the air or the feed upon idling is not permanently set but is regulated in accordance with the variations in the idling speed. For this purpose, a solenoid is acted on by a setting current which is formed, inter alia, as a function of the actual speed of rotation and effects such a displacement of the valve element connected to the solenoid that the actual speed of rotation reaches a predetermined desired speed substantially independently of any disturbing variables.
Specifically, known devices for regulating the idling speed are developed in such a manner that when the solenoid is without current the valve element is held, for instance, in closed position by the return spring. Only when the solenoid is acted on by the setting current does the valve element move in opposition to the force of the return spring into a middle position between the fully open and fully closed positions, until equilibrium of forces prevails between the magnetic force and the force of the return spring.
As a rule, the valve element is developed as an impact plate which is movable against knife edges of an idling-air passage opening.
It is desirable to adjust by means of the setting member a minimum mass flow of air, which may, for instance be less than 2 kg/hour. However, the minimum mass flow of air is limited by the fact that, in the prior art development of the devices, every movement of the solenoid as electric drive member was transmitted in rigid fashion to the valve element or an impact plate as sealing member. If, in such an arrangement, the sealing member is moved dynamically against a sealing edge or knife edges, then the sealing member rebounds from the sealing edge and thus produces an undesired opening.
It is an object of the invention so to improve a device of the aforementioned type for regulating the idling speed that it operates accurately, and in particular without rebound, even within the region of small air flows which are to be be set.